In a process for electrolytic refining of a metal such as copper or the like, and in particular in a long duration electrolytic refining and electrolytic sampling process, an electrode plate which is made from a metal such as stainless steel or the like is utilized as the cathode. This cathode is fitted into an electrolytic tank along with an anode which is made of blister copper or the like and electrolytic solution is filled therein; electrolysis is performed so that metal is precipitated and electrodeposited on both sides of the electrode plate. This is ablated so as to obtain the refined product in plate form (in the following, this precipitated and electrodeposited substance will be termed electrodeposited cathode material).
FIG. 8 and FIG. 9 are figures which show examples of the electrode plate; in these electrode plates 1, edge insulation members 2 are fitted on the circumferential edge portions of the electrode plates, so as to prevent the electrodeposited cathode material which is electrodeposited on both the sides of the electrode plate 1 from being connected to the edge portions of the electrode plate 1, and moreover so as to make it easy to ablate the electrodeposited cathode material, and further so as to ensure that it does not come into contact with both the cathodes.
As this type of edge insulation member 2, there are suggested, for example, ones such as those shown in FIG. 10 and FIG. 11. This type of edge insulation member 12 is one in which a fitting groove 13 and a jaw portion 14 for fixing the electrode plate are formed in its tip portion, so as to extend along the lengthwise direction of the edge insulation member 12.
When fitting this type of edge insulation member 12 to the electrode plate 1, the edge portion of the electrode plate 1 is inserted into the fitting groove 13, and is fixed in ten or more places with round pins 15. At this time, the edge insulation member 12 is fixed to the electrode plate 1 by fixing the edge insulation member 12, using insertion holes which are already formed in advance at predetermined positions in the edge insulation member 12 and the edge portion of the electrode plate 1, by fitting the electrode plate 1 so that these insertion holes are superimposed upon one another, by inserting the round pins 15 into these insertion holes, and by fusing the head portions of the round pins 15.
This type of edge insulation member 12 and round pins 15 may be made from a common resin such as vinyl chloride, polypropylene or the like.
Furthermore, in order to fill in any gap between the electrode plate 1 and the edge insulation member 12 which may be caused by deformation or thermal expansion or the like of the resin from which the edge insulation member 12 is made, and in order to close up the tightly fitting portion of the edge insulation member 1 against the electrode plate 1, wax 16 is flowed over this portion and solidified, so that it is ensured that no electrolytic solution can insinuate itself into this tightly fitted portion.
However, there are the following problems with this type of edge insulation member 12.
In the first place, since, along with it being necessary to form the wax portion 16 each time the edge insulation member 12 is fixed to the electrode plate 1, also it is necessary to remove the wax 16 each time the process of ablation of the electrodeposited cathode material from the electrode plate 1 is performed, accordingly the work involved in each process has become onerous, and the removal and fitting of the edge insulation member 12 to the electrode plate 1 has been very troublesome.
In the second place, it sometimes has happened that the quality of the refined material which is obtained during the electrolytic refinement process has been deteriorated, due to some of the wax 16 undesirably adhering or mixing in to the electrodeposited cathode material.
In the third place, since the thermal deformation coefficient of the resin from which the edge insulation member 12 is formed is large, accordingly the quality of secure engagement between the edge insulation member 12 and the electrode plate 1 is bad, and it is necessary to fix a large number of places with the round pins 15 as described above, so that the work becomes complicated and also excess cost is generated.
In the fourth place, since the head portions of the round pins 15 are fused to the edge insulation member 12, accordingly removal of the round pins 15 from the edge insulation member 12 has been troublesome. Furthermore, it has not been possible to reuse the edge insulation member 12 after the round pins 15 have been removed.
In the fifth place, it has sometimes happened that the round pins 15 have been broken away from the edge insulation member 12 due to shock when ablating the electrodeposited cathode material from the electrode plate 1.
In the sixth place, it has sometimes happened that electrolytic solution has permeated from the gap of the pin insertion holes of the edge insulation member 12 and the electrode plate 1, and that electrodeposited material which has accreted upon the electrode plate 1 has caused failure of the edge insulation member 12 and of the round pins 15.
In this manner, with a prior art edge insulation member 12, not only is the process of fitting and removal to the electrode plate 1 troublesome, but the quality of secure engagement to the electrode plate 1 has been inadequate; and even with a fixing method for supplementing this, in other words even with attachment with pins as well, it is necessary to form them in large numbers, and furthermore the work is complicated, and yet further there have been problems with the insulation characteristics of such portions. Furthermore, the anti impact characteristics and so on have deteriorated in strength. Even furthermore, there has been the problem that the quality of the refined product has been undesirably deteriorated by the use of the wax 16.